This invention relates to a parallel transport apparatus provided with a function of detecting the multiple feeding of sheets transported side by side along a plurality of transport paths.
There have been known image forming apparatuses including copying machines and printers. In these image forming apparatus, sheets contained in a cassette are dispensed therefrom by a feed roller and are transported to a pair of separation rollers including a forward roller rotating along with the transport of sheets and a retard roller rotating against the transport of sheets. The fed sheets are separated by the separation rollers and are transported one by one to a specified position where registration rollers are arranged.
Downstream from the separation rollers is arranged a multifeed sensor for detecting the multiple feeding of sheets. In other words, there is arranged such a sensor as to confirm whether two or more sheets have been fed by the feed roller while being placed one over another. If the multiple feeding of sheets is detected, the rotation of the feed roller is stopped and a multifeed state is cleared manually, i.e., the sheets placed one over another are removed manually.
Recently, there has been known a printer, or like image forming apparatus in which data such as addresses output from a data storage provided in a personal computer are printed. In the image forming apparatus of this type, two stacks of sheets are contained side by side in the cassette. After the sheets are fed side by side from the cassette, toner images formed on a photosensitive member or the like are transferred to the sheets being transported side by side.
In this image forming apparatus including a parallel transport apparatus, the probability that the multiple feeding of sheets occurs increases as much as the number of transport paths is increased. If the multiple feeding occurs along either one of the transport paths, the rotation of the feed roller is stopped to clear the multifeed state. In addition, it is required to adjust the synchronization with the feed of sheets along the other transport path again. Accordingly, it has been very cumbersome to clear the multifeed state at an occurrence of the multiple feeding, compared to a sheet transport apparatus in which the sheets are transported along only a single transport path.
Further, if the rotation of the feed roller is stopped at each occurrence of the multiple feeding, the image forming apparatus cannot meet a recent demand of users to carry out a printing operation at a high speed. Thus, a device for transporting the sheets in the multifeed state automatically has been desired earnestly.